By Eric Messinger

Published: April 2, 2000

Sometimes on MTV's ''Total Request Live,'' there is a contest to guess the identity of a music group based on a teasing snippet from one of its videos. Because thousands and thousands of the show's teenage viewers phone in, just being the one who makes it through is itself a triumph. But when Christina from Massachusetts called one Friday, her voice conveyed none of the usual excitement. If anything, she sounded sad and unsure of herself.

''Everything all right in your life?'' asked the show's host, Carson Daly. ''Can I help you, like, in 20 seconds to make things better?''

''I'm just very happy to be talking to you,'' Christina answered meekly.

Daly offered the hesitant teenager some classic rock-'n'-roll medicine. He told her to put on a CD by Korn (a very of-the-moment rap-metal band) and ''play it really, really loud, let all that energy out and start moshing in your room.''

Christina didn't promise anything, but Daly seemed to have to emboldened her. She asked if she might ''give a shout out'' to her science class. ''They didn't think I'd be able to get through to you,'' she explained.

The audience snickered, but not Daly. ''No, hey, that's cool,'' he said. ''You made it, didn't you? And you know what, Christina? They're playing with their Bunsen burners right now, and you're on 'T.R.L.'!''

Although might not know it to look at him, Carson Daly occupies a powerful perch at the intersection of television, popular music and youth culture. ''Total Request Live,'' or ''T.R.L.,'' as it is known to its legion of fans, retools an old promotional concept -- the Top 10 music countdown -- with a Gen-Y twist: interactivity. ''T.R.L.'' is broadcast live each weekday afternoon at 3:30 (just when most kids have arrived home from school), and the videos are selected not by MTV's music programmers but by viewers who phone or e-mail the network.

Not only do teenagers tune in and vote in large numbers, they also make pilgrimages from across the country to Times Square, where, overlooking Broadway at 45th Street, the ''T.R.L.'' studio is set up in a gigantic window display on the second floor of MTV headquarters. Although the show has a studio audience, additional fans crowd outside on the sidewalk, shouting and waving and jumping as the cameras pan over them. With a little high-tech help, the kids on Broadway even get to be in the videos; while a clip airs, selected teenagers appear in a corner of the screen to state why they like the song -- and then cheer very, very loudly. It's the 15-minutes-of-fame principle compacted into a piercing 15 seconds.

''Hi, I'm Terri from New York,'' said a lively brown-haired girl on one show, ''and I picked Christina Aguilera's 'What a Girl Wants' because you guys out there have to give us what we want! Yeaaaaaaaah!''

''Yeaaaaaaaah!'' screamed a chorus of girls around her.

MTV -- now an 18-year-old itself -- has always been a station of youth, of course, though in the past decade, the network has had to cope with some growing pains. While music was MTV's ostensible reason for being, showing videos never attracted the high ratings of nonmusic offerings like the ''The Real World.'' Only three years ago, some MTV executives began wondering if the time had come for the network to switch its focus from music to general-interest youth fare.

Daly's show has put an end to that kind of thinking. By giving viewers exactly the music they want, ''T.R.L.'' has given MTV the ratings it wants. The program, which made its debut in September 1998, reaches more than one million viewers, a huge audience for an afternoon cable show. For advertisers in search of record-buying, movie-going, clothes-shopping, trendsetting and trend-following youth, it is -- as some of its viewers might say -- the bomb. For record companies, it is nuclear.

Barry Weiss, the president of Jive Records, the label behind teen-fueled phenomenons like Backstreet Boys and Britney Spears, said: '' 'T.R.L.' is the sizzle on the channel, and a huge catalyst for sales. It's 'American Bandstand,' and Carson Daly is Dick Clark.'' When some group's or singer's video shows up on the ''T.R.L.'' countdown, said Geoff Mayfield of Billboard magazine, it's not long before that artist starts selling ''millions of records.'' As Mayfield put it, '' 'T.R.L.' is the thing -- not the only thing but a key thing -- that gets you from here to there.''

''Hey Carson! can I stand up there with you? Otherwise my mother won't believe I was here.''

''Carson, Carson, it's the birthday of my best friend from home, so will you let me do a shout out to her?''

Even during commercials, Daly gets besieged by requests. For a frantic three minutes following his phone chat with Christina, he walked around the show's small studio, offering smiles, hugs, handshakes, autographs.

''I can't believe I'm meeting you!'' exclaimed one young man with a spiky dog collar around his neck.

''Hey, I can't believe I'm meeting you,'' Daly responded. It was a remark that sailed right over the limits of credulity but probably gained him a fan for life.